This disclosure relates to short recoil weapons, and more particularly to the Browning M2 0.50 caliber (including all variants) and Browning 1919 0.30 caliber machine guns.
Short recoil weapons are generally configured to lock a bolt and a barrel together for a predetermined distance to ensure that energy produced by a fired cartridge is dissipated to a safe level prior to opening a breech. Prior to firing, a breech lock disposed in the barrel extension selectively engages a corresponding locking surface of the bolt (also described as the bolt lock interface), locking the bolt and barrel together. After the round is fired, the bolt, barrel extension and barrel travel together the predetermined distance. Then the breech lock disengages the bolt allowing the bolt to accelerate toward the rear of the receiver independently of the barrel.
While the bolt and the barrel are locked together and after the weapon is fired, a substantial portion of the recoil force is communicated to the locking surface of the bolt adjacent to the breech lock recess. Accordingly, a common wear point is the locking surface due to high cyclic rates of fire. After the amount of wear of the locking surface exceeds a predetermined wear threshold, the weapon may become dysfunctional or unsafe for use. Accordingly, even though only a small portion of the bolt is worn or distressed beyond allowable limits, the entire bolt is generally discarded.